1. Field of the Invention
The present invention relates to a storage battery which generates and stores electrical energy when there is a temperature difference, and discharges the electrical energy when there is no temperature difference. The battery can be used effectively in a wide variety of cases of thermal to electrical energy conversion utilizing heat sources such as plant waste heat, fuel cell heat, automotive-based heat such as exhaust gases and engine heat, hot springs, geothermal heat, solar heat, oceanic heat, facilities waste heat, incinerators, air conditioning equipment, radioisotopes and atomic reactors.
2. Technical Background
Conventionally, thermal/electrical energy converters based on temperature difference electrochemical batteries have been known. Such batteries comprise, as shown in FIG. 9, a low-temperature electrode 1, a high-temperature electrode 3, and disposed between the electrodes 1, 3, is a solution 2 containing redox ion couples which undergo a reversible charge transfer reaction between the electrode. A low-temperature medium 4 and a high-temperature medium 5 generate a temperature difference between the low-temperature electrode 1 and the high-temperature electrode 2, and an electromotive force (emf) is generated between the electrodes 1, 3.
If ferrocyanide and ferricyanide are used as the redox ion couple, for example, the following reactions take place, respectively, at the low-temperature electrode 1 and at the high-temperature electrode 3. The thermoelectric power generation is performed by negative ions (negative thermoelectric power generation), and the result is that the low-temperature electrode 1 becomes a positive electrode, and the high-temperature electrode 3 becomes a negative electrode. EQU Fe(CN).sub.6.sup.3- +e.sup.- .fwdarw.Fe(CN).sub.6.sup.4- (LT Electrode 1, Positive) EQU Fe(CN).sub.6.sup.4.sup.- .fwdarw.Fe(CN).sub.6.sup.3- +e.sup.- (HT Electrode 3, Negative)
As shown above, at the low-temperature positive electrode, Fe(CN).sub.6.sup.4- ions are generated, and at the high-temperature negative electrode, Fe(CN).sub.6.sup.3- ions are generated. The generated ionic species migrate to their respective electrode by mechanisms such as diffusion and thermal convection, thereby establishing a steady state electrochemical reaction between the electrodes 1, 3 and causing an electric current to flow when a load is connected therebetween.
In such a temperature difference battery, when the temperature difference ceases to exist by stopping the circulation of heating medium, the battery loses not only the ability for generating an emf but also its ability to deliver a flow of electric current.